Process of producing lead pigments.



ALEXANDER S. RAMAGE, 0F BUFFALO, NEW YORK, ASSIGNOR TO INTERNATIONAL COLOR & CHEMICAL COMPANY, INCORPORATED, 0F DETROIT, MICHIGAN, A COR- PORATION OF NEW YORK.

PROCESS OF PRODUCING LEAD PIGMENTS.

No Drawing.

To all whom z't may concern:

Be it known that I, ALEXANDER S. RAMAGE, a subject of the King of Great'Britain, residing at Buffalo, in the county of Erieand State of New York, .have invented certain new and useful Improvements in Processes of Producing Lead Pigments, of which the following is a specification.

This invention is a process whereby lead pigments, including white lead, may be prepared directly from sulfid ores of lead, or from Waste products containing lead sulfate.

According to the invention, le'a'd sulfid ore is roasted under conditions to yield lead-oxid and lead sulfate, the latter in the minimum practicable proportions. Theseroasting conditions are well understood in the art and need not therefore be described.

The roasted ore is then treated with a hot solution of sodium carbonate, a ten per cent. solution being suitable, used in sufficient excess to convert the lead-sulfate to lead carbonate. In practice, it is found that sodium carbonate in about one-third excess over the amount required by theory is suflicient for this purpose. dium sulfate'and the excess of sodium carbonate may be drawn off and employed in the treatment of another batch of ore.

The residue consisting essentially of lead oxid and lead carbonate is dissolved in a dilute solution of caustic soda. For this purpose a five per cent. solution of NaOH has been found suitable, tity that 100 parts of .the said solution are present for each 2.8 parts of PhD in the lead-bearing product.

The resulting solution is clarified h settling and its lead contents are precipitated by carbon dioxid, preferably using for this purpose the gases derived from a lime kiln. The solution is heated to drive ofl any excess of carbon dioxid, and to insure that no bicarbonate remains in solution. The recipitated lead carbonate is then filtered ofl', thoroughly washed, and converted into basic carbonate by the addition of sodium hy- Speciflcation of Letters Patent.

The solution containing so-.

used in such quan proportion'required by the equation The basic carbonate of lead or white lead thus produced is thoroughly washed and constitutes the immediate product of the process. arising in the precipitation of the lead carbonate by carbondioxid, and in the conver-. v sion of this lead carbonate to the basic salt by caustic soda, are combined, and causticized with lime. For this 'purpose, the lime from which the carbon dioxid has been driven off is available.

If desired, the white lead formed as above may be converted by appropriate further treatment into basic chromate of lead. I

Instead of starting with a mixture of lead oxid and sulfate derived'from a sulfid ore as aforesaid, I may use as a starting material the waste lead sulfate from sulfuric acid chambers or other sources.

Patented Oct. 23, 1917. Application filed January s, 1916. Serial No. 70,992.

The sodium carbonate solutions,

l. The process of producing precipitated lead pigments which consists in reacting upon a material containing lead sulfate with an aqueous solution of a carbonate, thereby ing lead carbonate by carbon dioxid.

2. The process of producing precipitated lead pigments which consists in roasting a.

sulfid ore of lead under conditions to-form oxid and sulfate of lead, treating the roasted product with an aqueous solution of a caronate and thereby converting the sulfate of lead into carbonate, dissolving the mixed oxid and carbonate in caustic alkali solution and re-precipitating lead carbonate by car- .bon dioxid.

3. The process of producing lead pigments which consists in reactmg upon a material containing lead sulfate with an aqueous solution of a carbonate,

forming lead carbonate, dissolving the same thereby in caustic alkali solution and re-precipitat ing bycarloon olioxidl, and thereafter converting the precipitated. carbonate into a basic salt by treatment With caustic alkali.

The process of prodncing lead pigments which consists in roasting a sulfiol ore of lead under conditions to form oxicl aria sulfate of leaol, treating the roasted product with an aqueous solution of a carbonate ancl thereby converting the sulfate of lead into carbonate olissolving the mixed oXiol an.

i aaegzca carbonate in caustic alkali solution and re- I vinto a basic salt by treatment With. caustic alkali.

In testimony Whereoi ll aiiix my signature in presence of two Witnesses ALEXANDER S. RAMAGEQ Witnesses:

FLORENCE Jaoonr, CHARLEs lfinmt 

